Bearing isolator seals are commonly used in a variety of rotating shaft applications when it is necessary to exclude contaminants or process fluid from reaching internal mechanisms such as shaft support bearings, or from leaking out of a housing that is penetrated by the rotating shaft.
For example, bearing isolator seals are used in bearing housings for pumps, motors, gearboxes and other pieces of rotating equipment. The main purpose of a bearing isolator seal is to prevent the ingress of process fluid or other contaminants into the bearing, which can lead to premature failure of the lubrication and bearings. In fact, penetration by contaminants is the most common reason for rotating equipment failure.
For many applications, lip seals and simple labyrinths have proven inadequate for preventing ingress of contamination into bearings. In many cases, the use of bearing isolator seals can extend rotating equipment lifespans by a factor of 2 to 5, as compared to the typical equipment lifespans when standard lip seals or simple labyrinths are used.
Bearing isolators use a stator in close proximity to a dynamic rotor to prevent the ingress of contamination. Rotors are typically driven by the rotating shaft, and are usually coupled to the shaft by a drive O-ring that transmits torque from the shaft to the rotor. The grip of the drive O-ring is critical to the stability of the rotor, and to the performance of the bearing isolator.
Due to a need for compactness, among other considerations, most bearing isolators use a single drive O-ring in a single groove to couple the rotor to the shaft. An example of this approach is shown in FIG. 1, which includes a single rotor drive ring 100. However, for some applications this approach does not provide sufficient rotor stability and performance. In particular, a single drive O-ring may fail to maintain the alignment of the rotor with the stator to within acceptable tolerances for some applications.
With reference to FIG. 2, some bearing isolators include 2 drive O-rings 200, 202 in two separate grooves 204, 206. This approach can provide better rotor alignment, stability and performance than a single drive O-ring, but significant elongation of the rotor is required to accommodate the two drive O-rings and grooves. Accordingly, this approach may not be suitable for applications that require a compact solution.
What is needed, therefore, is a bearing isolator seal that provides enhanced shaft grip and rotor alignment stability without undue loss of compactness.